provide useCurrentApp skeleton (#846)
provide useCurrentApp skeleton (#846)

`useCurrentApp` is maybe a nice idea, but we should avoid bloating our
already gigantic application with even more features until we're sure we
actually need 'em.

This change includes a commented example implementation. Maybe 
a future implementor will find it useful. 
folio-org/stripes-core,folio-org/stripes-core,folio-org/stripes-core